MGBetts

Thanks for that, I think you're probably right - the car is still in warranty, so I'll take it to my local Citroën dealer first - I'll mention what you've said (though knowing what garages are like, they probably won't want to hear it!)

I just brought a 2006 Citroen C5 Exclusive HDI Est, 1997cc, and I have been finding that when vehicle is first started up the brake servo doesn't work and the brake pedal is "hard". This only happens at low speeds/revs and after a short while it is OK. But it has led to a few scary moments when I thought my brakes had failed. Any ideas?